Rep. Henry Cuellar (center), D-Laredo, along with U.S. Customs and Border Protection Commissioner Alan Bersin (right) and Director of Operations for the Sierra Vista, Arizona office David Gasho (left) chat in

WASHINGTON — Ever since Iranian President Mahmoud Ahmadinejad struck a deal with Venezuelan leader Hugo Chávez for weekly air service between the nations' distant capitals, American officials have worried that Iranian-backed terrorists could reach to the rim of Latin America, pick up fake Venezuelan passports and sneak into the United States.

Now, with growing talk of a pre-emptive attack by Israel to slow Iran's suspected nuclear-weapons program, Iran has threatened that it would retaliate across the globe. And Iran's easy access to the Western Hemisphere has U.S. officials particularly concerned.

The commercial service between Tehran and Caracas by Iran Air and Conviasa Air Venezuela, including a stop in Damascus, Syria, is so secretive that there's confusion among intelligence agencies about whether the flights are continuing. Israeli experts believe they are; U.S. officials aren't so sure.

“Some Iranian officials — probably including Supreme Leader Ali Khamenei — have changed their calculus and are now more willing to conduct an attack in the United States in response to real or perceived U.S. actions that threaten the regime,” James Clapper, director of national intelligence, warned the Senate Intelligence Committee in his latest worldwide threat assessment.

If that attack comes, experts see it being staged by Iranian operatives who entered the U.S. through Latin America.

“There's pretty much of a general consensus within the intelligence community that Iranian-backed cells providing financial support to Hezbollah could easily convert to operational cells and light up the place,” said U.S. Rep. Michael McCaul, R-Austin.

“From our observations on this trip, the Iranian threat to the United States is very real, and it would be difficult to defend against all of these operatives.”

Iranian retaliation would likely fall to pre-positioned operatives drawn from the ranks of the 15,000-strong Iranian Revolutionary Guards Quds Force or 10,000-member, Iranian-backed Hezbollah, based in southern Lebanon.

Raising money

McCaul said Hezbollah is fundraising with impunity in the tri-border area surrounded by Paraguay, Argentina and Brazil, where an estimated 30,000 Lebanese expatriates and immigrants live among a population of 800,000.

He said enterprising businesses there, some importing counterfeit products from China for resale in Latin America, are being required to tithe as much as 2 percent of gross revenue to the terrorist organization.

Yet the suspected terrorist safe haven is largely ignored by law enforcement from the three adjacent countries.

“Authorities downplay the threat,” McCaul said. “They talk about trans-national crime. But they don't want to talk about terrorism. If you use the T-word, they pucker up.”

The suicide bombing of an Israeli tourist bus in Bulgaria on July 18, killing five Israelis and wounding 30, is the latest sign that Tehran remains prepared to strike abroad. The suspected Hezbollah bombing coincided with the 18th anniversary of the organization's 1994 attack on a Jewish community center in Argentina that killed 85 people. A similar attack two years earlier in Argentina killed 29 civilians.

“Iran has methodically cultivated a network of sponsored terrorist surrogates capable of conducting effective, plausibly deniable attacks against Israel and the United States,” the Pentagon's latest assessment of Iran's military power said.

Forging ties

At the same time, there are signs that Iranian agents are forging ties with murderous, multibillion-dollar Mexican drug cartels.

“Iranian operatives are stepping into power vacuums,” said Rep. Henry Cuellar, D-Laredo, a member of the House Committee on Homeland Security who made the trip.

Federal authorities unmasked an alleged Iranian Quds Force plot last fall that featured attempts by a naturalized U.S. citizen born in Iran to enlist a member of the Mexican narco-terrorist organization Los Zetas in a $1.5 million scheme to assassinate the Saudi ambassador to the United States.

Facing trial

Manssor Arbabsiar, a Texas resident arrested Sept. 29 at John F. Kennedy International Airport, faces trial in New York in October on multiple charges stemming from the alleged plot to kill Adel Al-Jubeir by bombing his favorite restaurant in Washington, D.C.

McCaul said Iranian operatives planned to synchronize the bombing in Washington, D.C., with simultaneous attacks on the Saudi and Israeli embassies in Buenos Aires, Argentina.

“We have to presume that Hezbollah cells are present and being fortified while awaiting orders from Iran,” retired Marine Col. Timothy Geraghty warned Congress last fall after the assassination plot came to light.

Congressional investigators working for the GOP majority estimate that there are “at least hundreds of Hezbollah operatives” within the United States, according to Rep. Peter King, R-N.Y., the chairman of the Republican-led House Committee on Homeland Security.

“In light of last year's bomb plot, in light of the 20 Hezbollah cases prosecuted since 9/11 and in light of Hezbollah attacks overseas, we have a duty to prepare for the worst,” King added.

Just as the 19 suicide hijackers who carried out the 9/11 attacks arrived at U.S. airports with valid travel documents, most suspected Iranian operatives are believed to have entered the U.S. through the 327 ports of entry, including airports, border crossings and maritime ports.

A handful may have surreptitiously crossed the 1,969-mile southwestern border, smuggled into the United States with tens of thousands of undocumented immigrants from Mexico and other countries who cross the boundary every year.

Of 59,017 non-Mexican citizens who were arrested crossing the U.S.-Mexico border in 2010, 14 came from Iran and 11 from Lebanon, Hezbollah's base of operations.